! Copyright (C) 2011
! Free Software Foundation, Inc.
!
! This file is part of the gtk-fortran gtk+ Fortran Interface library.
!
! This is free software; you can redistribute it and/or modify
! it under the terms of the GNU General Public License as published by
! the Free Software Foundation; either version 3, or (at your option)
! any later version.
!
! This software is distributed in the hope that it will be useful,
! but WITHOUT ANY WARRANTY; without even the implied warranty of
! MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
! GNU General Public License for more details.
!
! Under Section 7 of GPL version 3, you are granted additional
! permissions described in the GCC Runtime Library Exception, version
! 3.1, as published by the Free Software Foundation.
!
! You should have received a copy of the GNU General Public License along with
! this program; see the files COPYING3 and COPYING.RUNTIME respectively.
! If not, see <http://www.gnu.org/licenses/>.
!------------------------------------------------------------------------------
! Contributed by: James Tappin
! PLplot code derived from PLplot's example 1 by Alan W. Irwin
! Last modifications: vmagnin 2020-06-10 (GTK 4), 2020-07-13
!------------------------------------------------------------------------------

module common_ex1
  use, intrinsic :: iso_c_binding
  use gtk, only: gtk_widget_show, gtk_window_set_child, gtk_window_destroy
  use gtk_draw_hl
  use plplot_extra

  integer(c_int) :: height, width
  type(c_ptr) :: window
  type(c_ptr) :: my_gmainloop
end module common_ex1

module plplot_code_ex1
  use plplot, PI => PL_PI
  use common_ex1

  implicit none
  real(plflt) :: xscale, yscale, xoff, yoff

contains
  subroutine x01f95(area)

    type(c_ptr), intent(in) :: area
    type(c_ptr) :: cc
    character(len=80) :: version
    character(len=20) :: geometry
    integer :: digmax

    ! needed for use as functions instead of subroutines
    integer :: plparseopts_rc
    integer :: plsetopt_rc

    ! Define colour map 0 to match the "GRAFFER" colour table in
    ! place of the PLPLOT default.
    integer, parameter, dimension(16) :: rval = [255, 0, 255, &
         & 0, 0, 0, 255, 255, 255, 127, 0, 0, 127, 255, 85, 170],&
         & gval = [ 255, 0, 0, 255, 0, 255, 0, 255, 127, 255, 255, 127,&
         & 0, 0, 85, 170], &
         & bval = [ 255, 0, 0, 0, 255, 255, 255, 0, 0, 0, 127, 255, 255,&
         & 127, 85, 170]

    !  Process command-line arguments
    plparseopts_rc = plparseopts(PL_PARSE_FULL)
    if (plparseopts_rc /= 0) stop "plparseopts error"

    !  Print plplot version
    call plgver(version)
    write (*,'(a,a)') 'PLplot library version: ', trim(version)

    ! Get a cairo context from the drawing area.
    cc = hl_gtk_drawing_area_cairo_new(area)

    !  Initialize plplot
    call plscmap0(rval, gval, bval)
    call plsdev("extcairo")

    ! By default the "extcairo" driver does not reset the background
    ! This is equivalent to the command line option "-drvopt set_background=1"
    plsetopt_rc = plsetopt("drvopt", "set_background=1")
    if (plsetopt_rc /= 0) stop "plsetopt error"

    ! The "extcairo" device doesn't read the size from the context.
    write(geometry, "(I0,'x',I0)") width, height
    plsetopt_rc = plsetopt( 'geometry', geometry)
    if (plsetopt_rc /= 0) stop "plsetopt error"

    !  Divide page into 2x2 plots
    call plstar(2,2)

    ! Tell the "extcairo" driver where the context is located. This must be
    ! done AFTER the plstar or plinit call.

    call pl_cmd(PLESC_DEVINIT, cc)

    !  Set up the data
    !  Original case
    xscale = 6._plflt
    yscale = 1._plflt
    xoff = 0._plflt
    yoff = 0._plflt

    !  Do a plot
    call plot1()

    !  Set up the data
    xscale = 1._plflt
    yscale = 0.0014_plflt
    yoff = 0.0185_plflt

    !  Do a plot
    digmax = 5
    call plsyax(digmax,  0)
    call plot1()

    call plot2()
    call plot3()

    !  Don't forget to call PLEND to finish off, and then delete the
    !  cairo context.
    call plend()
    call hl_gtk_drawing_area_cairo_destroy(cc)

  end subroutine x01f95

  !======================================================================
  subroutine plot1()

    real(plflt), dimension(1:60) :: x, y
    real(plflt), dimension(1:6)  :: xs, ys
    real(plflt) :: xmin, xmax, ymin, ymax
    integer :: i

    do i = 1, 60
       x(i) = xoff + xscale * dble(i)/60.0_plflt
       y(i) = yoff + yscale * x(i)**2
    enddo

    xmin = x(1)
    xmax = x(60)
    ymin = y(1)
    ymax = y(60)

    do i = 1, 6
       xs(i) = x((i-1)*10+4)
       ys(i) = y((i-1)*10+4)
    enddo

    !   Set up the viewport and window using PLENV. The range in X is
    !   0.0 to 6.0, and the range in Y is 0.0 to 30.0. The axes are
    !   scaled separately (just = 0), and we just draw a labelled
    !   box (axis = 0).

    call plcol0(1)
    call plenv( xmin, xmax, ymin, ymax, 0, 0 )
    call plcol0(2)
    call pllab( '(x)', '(y)', '#frPLplot Example 1 - y=x#u2' )

    !   Plot the data points
    call plcol0(4)
    call plpoin( xs, ys, 9 )

    !   Draw the line through the data
    call plcol0(3)
    call plline( x, y )

  end subroutine plot1

  !======================================================================
  subroutine plot2()

    real(plflt), dimension(1:100) :: x, y
    integer :: i
    !
    !   Set up the viewport and window using PLENV. The range in X is
    !   -2.0 to 10.0, and the range in Y is -0.4 to 2.0. The axes are
    !   scaled separately (just = 0), and we draw a box with axes
    !   (axis = 1).
    call plcol0(1)
    call plenv(-2.0_plflt, 10.0_plflt, -0.4_plflt, 1.2_plflt, 0, 1 )
    call plcol0(2)
    call pllab( '(x)', 'sin(x)/x', '#frPLplot Example 1 - Sinc Function' )

    !   Fill up the arrays
    do i = 1, 100
       x(i) = (i-20.0_plflt)/6.0_plflt
       y(i) = 1.0_plflt
       if (x(i) /= 0.0_plflt) y(i) = sin(x(i)) / x(i)
    enddo

    !   Draw the line
    call plcol0(3)
    call plwidth(2.0_plflt)
    call plline( x, y )
    call plwidth(1.0_plflt)

  end subroutine plot2

  !======================================================================
  subroutine plot3()
    !
    !   For the final graph we wish to override the default tick intervals,
    !   and so do not use_ PLENV
    real(plflt), dimension(1:101) :: x, y

    integer i
    call pladv(0)

    !   Use_ standard viewport, and define X range from 0 to 360 degrees,
    !   Y range from -1.2 to 1.2.
    call plvsta()
    call plwind( 0.0_plflt, 360.0_plflt, -1.2_plflt, 1.2_plflt )

    !   Draw a box with ticks spaced 60 degrees apart in X, and 0.2 in Y.
    call plcol0(1)
    call plbox( 'bcnst', 60.0_plflt, 2, 'bcnstv', 0.2_plflt, 2 )

    !   Superimpose a dashed line grid, with 1.5 mm marks and spaces. With
    !   only a single mark and space element, we do not need arrays
    call plstyl( [1500], [1500] )
    call plcol0(2)
    call plbox( 'g', 30.0_plflt, 0, 'g', 0.2_plflt, 0 )
    !   remember from the error message:
    !   plstyl: At least one mark or space must be > 0, aborting operation
    call plstyl( [0], [1] )

    call plcol0(3)
    call pllab( 'Angle (degrees)', 'sine', '#frPLplot Example 1 - Sine function' )

    do i = 1, 101
       x(i) = 3.6_plflt * (i-1)
       y(i) = sin( x(i) * PI/180.0_plflt )
    enddo

    call plcol0(4)
    call plline( x, y )
  end subroutine plot3
end module plplot_code_ex1

module handlers_ex1
  use common_Ex1
  use gtk_hl_container
  use gtk_hl_button
  use gtk_draw_hl
  use, intrinsic :: iso_c_binding

  implicit none
  integer(c_int) :: run_status = TRUE
  real(c_double), parameter :: pi = acos(-1.0_c_double)

contains

  subroutine quit_cb(widget, gdata) bind(c)
    type(c_ptr), value, intent(in) :: widget, gdata
    call gtk_window_destroy(window)
  end subroutine quit_cb

  subroutine activate(app, gdata) bind(c)
    use plplot_code_ex1
    use gtk, only: gtk_application_window_new, gtk_window_set_title
    implicit none
    type(c_ptr), value, intent(in)  :: app, gdata
    ! Pointers toward our GTK widgets:
    type(c_ptr) :: drawing, scroll_w, base, qbut

    height = 1000
    width = 1200

    ! Create the window:
    window = gtk_application_window_new(app)
    call gtk_window_set_title(window, "PLplot x01 / gtk-fortran (extcairo)"//c_null_char)

    base = hl_gtk_box_new()
    call gtk_window_set_child(window, base)

    drawing = hl_gtk_drawing_area_new(size=[width, height], &
         & has_alpha = FALSE, &
         & scroll = scroll_w, &
         & ssize=[ 600, 500 ])
    call hl_gtk_box_pack(base, scroll_w)

    qbut = hl_gtk_button_new("Quit"//c_null_char, clicked=c_funloc(quit_cb))
    call hl_gtk_box_pack(base, qbut, expand=FALSE)

    call gtk_widget_show(window)

    call x01f95(drawing)
  end subroutine activate
end module handlers_ex1


program cairo_plplot_ex1
  use, intrinsic :: iso_c_binding, only: c_ptr, c_funloc, c_null_char
  use handlers_ex1
  use gtk_hl_container, only: hl_gtk_application_new
  implicit none
  type(c_ptr) :: my_app

  my_app = hl_gtk_application_new("gtk-fortran.plplot.hl_plplot1e"//c_null_char, &
                             & c_funloc(activate))
end program cairo_plplot_ex1

